An in vitro assessment of a ceramic-pressed-to-metal system as an alternative to conventional metal ceramic systems.

PURPOSE: This article reviews a press-on metal (POM) ceramic versus a conventional veneering system regarding marginal gaps, fracture resistance, microhardness, and surface roughness. This was done to provide clinical recommendations for its use. MATERIALS AND METHODS: Forty crowns were constructed and divided into two main groups according to the metal coping design. Group 1: Twenty metal copings with metal margin extending to the axiogingival line angle. Group 2: Twenty metal copings with metal margin 1 mm occlusal to the axiogingival line angle. The specimens of each group were further subdivided into two subgroups (A and B) according to the veneering porcelain used. The vertical marginal gaps of the crowns were measured after veneering placement. For fracture resistance testing, the crowns were subjected to compressive load to failure. Representative samples of the two main groups were selected to measure surface roughness and microhardness. RESULTS: No statistically significant difference was evident regarding the vertical marginal gap distance in relation to the margin design of both tested groups (p= 0.249, p= 0.815); however, the POM veneer group with metal porcelain margin showed statistically lower marginal gaps than the conventional ceramic veneer group (p= 0.043). Fracture resistance values did not show statistically significant difference regarding the margin design (p= 0.858, p= 0.659) or type of the ceramic veneer material (p= 0.592, p= 0.165). Both groups showed no significant difference in their mean roughness values (p= 0.235). Conventional ceramics showed statistically significantly higher mean microhardness values than POM did (p= 0.008). CONCLUSION: This study showed superior marginal adaptation, decreased microhardness, and similar load to failure and roughness values of the POM ceramic system. Moreover, considerable ease and speed of fabrication of this system were evident. The high variation in range values of some tested groups is among the limitations of this study, along with the lack of clinical trials to test the system in vivo.

Assessment of an indirect metal ceramic repair system.

PURPOSE: This study was designed to compare an alternative indirect treatment to repair fractured or chipped veneering metal ceramic using recently developed ultra-low-fusing ceramics. MATERIALS AND METHODS: One conventional feldspathic ceramic, Vita Omega, and three ultra-low-fusing ceramics (ULFC), Finesse, Duceram LFC, and Vision-low, were used. Forty ceramic specimens were prepared and divided into two groups. Group I (n = 20) was designed for bond strength testing. It comprised four subgroups (A, B, C, D): one Ceramic-resin (A) and three Ceramic-ULFC disc specimens of different diameters (B, C, D). Group II was composed of repaired ceramic discs using direct and indirect repair methods for biaxial testing. It was comprised of five subgroups: the fractured discs from subgroup A; Omega discs (n = 20) formed the repaired specimens of the four remaining subgroups: B, C, D, E. Data were presented as means and standard deviation (SD) values. One-way analysis of variance (ANOVA) was used for comparison between means. Tukey's post hoc test was used for pairwise comparison between the means when ANOVA test was significant. The significance level was set at p